Modular steerable sheath catheters

ABSTRACT

An apparatus for accessing a site within a body includes a cannula and an elongate member. The cannula has a proximal end, a distal end, and a lumen extending therebetween. The elongate member has a distal end configured for insertion into the lumen, wherein the distal end of the elongate member is attachable to and releasable from the distal end of the cannula. A method for accessing a site within a body includes inserting a distal end of an elongate member into a lumen of a cannula, detachably attaching the distal end of the elongate member to the cannula, and steering a distal end of the cannula to a desired site using the elongate member.

FIELD OF THE INVENTION

The present invention relates generally to catheters, and moreparticlarly to catheters that are used to provide access into a body fordelivery of additional tools, instruments, medications, or fluids.

BACKGROUND

Catheters have been used to reach locations within a body otherwiseunreachable without invasive surgery. A catheter has a distal end whichis configured to enter a patient, such as a major vein, artery, or otherbody cavity. Once the tip of the catheter is inserted into the patient,the catheter is distally advanced until the distal end of the catheterreaches a target site.

Steerable mechanisms have been developed to facilitate the transit ofcatheters through a patient's blood vessels. In practice, a surgeontypically observes the catheter fluoroscopically and maneuvers thecatheter by selective rotation and deflection of a steering mechanism ofthe proximal end of the catheter. The rotation and deflection at theproximal end bends or deflects the tip of the catheter and enables thesurgeon to steer the catheter as it advances through the tortious pathoften found during the transit through a patient's blood vessels.

In many applications, the ability to steer the catheter is crucial tothe success of a procedure and can be a factor in reducing risk to andtrauma of the patient. Moreover, the ability to steer the catheterimpacts the speed and ease by which the surgeon can properly positionthe distal end, particularly during heart mapping protocols.

The distal ends of some steerable catheters are formed of a shape memorymaterial or structure, such as a coil spring, so that the application ofa force to a steering cable (that is fixedly secured to a distal end ofthe catheter) deflects the distal tip of the catheter from its normalposition. As the tension in the cable is released, the distal end tendsto return to its normal position. The inclusion of the coil spring,cable, and other components of a steering mechanism at the distal end ofthe catheter imposes a limitation as to the smallest cross sectionaldimension that the catheter can have. In addition, for catheters thathave one or more working channels (e.g., for delivering fluids ortools), it may be difficult to secure the cable or other components ofthe steering mechanism to the distal end of the catheter in a way thatdoes not interfere operations of the catheter.

Accordingly, improved devices and methods for providing access within abody would be useful.

SUMMARY OF THE INVENTION

In accordance with an embodiment of the invention, an apparatus foraccessing a site within a body includes a cannula and an elongatemember. The cannula has a proximal end, a distal end, and a lumenextending therebetween. The elongate member has a distal end configuredfor insertion into the lumen, wherein the distal end of the elongatemember is attachable to and releasable from the distal end of thecannula. In one embodiment, the elongate member is a part of a steeringdevice that is configured to steer the distal end of the cannula. Inanother embodiment, the elongate member is a stiffening elementconfigured to increase a stiffness of the cannula.

In accordance with another embodiment of the invention, a method foraccessing a site within a body includes inserting a distal end of anelongate member into a lumen of a cannula, detachably attaching thedistal end of the elongate member to the cannula, and steering a distalend of the cannula to a desired site using the elongate member.

In accordance with another embodiment of the invention, a method foraccessing a site within a body includes inserting a distal end of afirst elongate member into a first lumen of a cannula to therebyincrease a stiffness of the cannula, detachably attaching the distal endof the first elongate member to the cannula, and manipulating a proximalend of the cannula to thereby place a distal end of the cannula at adesired position.

In accordance with another embodiment, a method for accessing a sitewithin a body includes inserting a wire having a bent configuration intoa lumen of a cannula, the cannula having a distal end, a first portionat the distal end, and a second portion proximal to the first portion,wherein the second portion is relatively stiffer than the first portion,and manipulating the wire by sliding a distal end of the wire eitherdistally or proximally relative to the cannula to thereby steer thedistal end of the cannula.

Other aspects and features of the invention will be evident from readingthe following detailed description of the preferred embodiments, whichare intended to illustrate, not limit, the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate the design and utility of preferred embodimentsof the present invention, in which similar elements are referred to bycommon reference numerals. In order to better appreciate how advantagesand objects of the present inventions are obtained, a more particulardescription of the present inventions briefly described above will berendered by reference to specific embodiments thereof, which areillustrated in the accompanying drawings. Understanding that thesedrawings depict only typical embodiments of the invention and are nottherefore to be considered limiting its scope, the invention will bedescribed and explained with additional specificity and detail throughthe use of the accompanying drawings.

FIG. 1A illustrates a catheter for providing access into a body inaccordance with an embodiment of the invention, which includes a cannulaand a steering device having an expandable member;

FIG. 1B illustrates the catheter of FIG. 1A, showing the expandablemember being inflated;

FIG. 1C illustrates a variation of a cross section of the catheter ofFIG. 1A, showing the expandable member having an elliptical crosssectional shape;

FIG. 2 illustrates a variation of the catheter of FIG. 1, particularlyshowing a lumen of a cannula that is off-center;

FIG. 3A illustrates a catheter for providing access into a body inaccordance with another embodiment of the invention, which includes acannula having an interior wall that can be expended radially inward;

FIG. 3B illustrates the catheter of FIG. 3A, showing the interior wallof the cannula compressing against a wire;

FIGS. 4A and 4B illustrate a catheter for providing access into a bodyin accordance with another embodiment of the invention, showing avariation of a steering device;

FIGS. 5A and 5B illustrate another variation of a steering device;

FIG. 6 illustrates a catheter for providing access into a body inaccordance with other embodiments of the invention, showing the catheterhaving a plurality of steering devices;

FIG. 7A illustrates a catheter for providing access into a body inaccordance with another embodiment of the invention, which includes aworking channel for housing a slidable steering wire;

FIG. 7B illustrates the catheter of FIG. 7A, showing a distal end of acannula being steered as the steering wire is advanced distally; and

FIG. 8 illustrates a catheter for providing access into a body inaccordance with another embodiment of the invention, showing thecatheter having a plurality of stiffening elements engaging with acannula.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Various embodiments of the present invention are described hereinafterwith reference to the figures. It should be noted that the figures arenot drawn to scale and that elements of similar structures or functionsare represented by like reference numerals throughout the figures. Itshould also be noted that the figures are only intended to facilitatethe description of specific embodiments of the invention. They are notintended as an exhaustive description of the invention or as alimitation on the scope of the invention. In addition, an illustratedembodiment needs not have all the aspects or advantages of the inventionshown. An aspect or an advantage described in conjunction with aparticular embodiment of the present invention is not necessarilylimited to that embodiment and can be practiced in any other embodimentsof the present invention even if not so illustrated.

FIGS. 1A and 1B illustrate a catheter 100 in accordance with anembodiment of the invention. The catheter 100 includes a cannula 102 anda steering device 120 that can be detachably secured to the cannula 102.

The cannula 102 has a proximal end 104, a distal end 106, and a lumen108 extending between the proximal and distal ends 104, 106. In theillustrated embodiment, the distal end 106 has a cross sectionaldimension that is between 0.7 mm and 1.2 mm, and more preferably between0.9 mm and 1.0 mm. However, the distal end 106 of the cannula 102 mayhave other dimensions, depending on a particular application. The distalend 106 of the cannula can also has a tapered profile to allow ease ofinsertion into a site, such as a vein, an artery, an incision, a burr,and a breast duct. The cannula 102 can further include a radiopaquemarker (not shown) secured to the distal end 106 of the cannula 102, oralternatively, a marker located at an exterior surface of the cannula102, to assist a placement of the distal end 106 of the cannula 102during use.

The cannula 102 can be made from a variety of materials, such as, ametal, an alloy, or a polymeric, electrically nonconductive material,like polyethylene, polyurethane, or PEBAX® material (polyurethane andnylon). Even more alternatively, the distal end 106 is made softer thanthe proximal portion of the cannula 102 by using different materialand/or having a thinner wall thickness. This has the benefit of reducingthe risk of injury to tissue that the distal end 106 may come in contactwith during an operation. In another embodiment, the cannula 102 canalso include a liner secured to an interior wall 158 of the cannula 102,the liner being composed of a suitable low friction material, e.g.,TEFLON®, Polyetheretherketone (PEEK), polyimide, nylon, polyethylene, orother lubricious polymer linings, to reduce surface friction with adevice as the device slides within the lumen 108. In some embodiments,the cannula can be made torsionally stiff enough such that 1 degree ofrotation at a proximal end creates a substantially 1 degree of rotationat the distal end. Also, in other embodiments, the cannula 102 canfurther include one or more openings or slots at the wall of the cannula102 to provide a desired flexural and/or torsional stiffness to thecannula 102. The openings or slots can extend partially or completelythrough a thickness of the wall of the cannula 102.

The steering device 120 is configured to removably secure to the distalend 106 of the cannula 102, and can be used to steer the distal end 106of the cannula 102 after the steering device 120 is secured to thecannula 102. As shown in the illustrated embodiment, the steering device120 includes a shaft 130 having a proximal end 132, a distal end 134,and a lumen 136 extending therebetween, and an expandable member 140secured to the distal end 134. In another embodiment, the steeringdevice 120 can further include a handle connected to the proximal end132 for adjusting or applying a tension force to the shaft 130. Any ofthe materials described previously with reference to the cannula 102 isalso suitable for construction of the shaft 130. In some embodiments,the shaft 130 can be made torsionally stiff enough such that 1 degree ofrotation at a proximal end creates a substantially 1 degree of rotationat the distal end. Also, in some embodiments, the shaft 130 can furtherinclude one or more openings or slots at the wall of the shaft 130 toprovide a desired flexural and/or torsional stiffness to the shaft 130.In the illustrated embodiment, the expandable member 140 is made from apolymer. However, the expandable member 140 can also be made from otherelastic materials. The expandable member 140 has a distal end 142 thatis secured to the distal end 134 of the shaft 130, and a proximal end144 that is secured to the shaft 130 at a point that is proximal to thedistal end 134. Such configuration provides axial stiffness to thesteering device 120 where the expandable member 140 is located, andprevents the expandable member 140 from buckling or collapsing as thedistal end 134 of the shaft 130 is advanced distally within the lumen108. Alternatively, the expandable member 140 can be constructed to havesufficient axial strength, and the proximal end 144 of the expandablemember 140 can be secured to the distal end 134 of the shaft 130.

As shown in FIG. 1A, the expandable member 140 has a low profile andforming a substantially continuous surface with the shaft 130 when in acollapsed configuration. The low profile of the expandable member 140allows ease of insertion and advancement within the lumen 108 of thecannula 102. During use, the expandable member 140 is advanced distallywithin the lumen 108 of the cannula 102 until the expandable member 140reaches the distal end 106 of the cannula 102 (or until the expandablemember 140 is desirably placed). Inflation fluid, such as saline or gasis then delivered via the lumen 136 of the shaft 130, and exits from oneor more openings 150 located on the shaft 130 to inflate the expandablemember 140 (FIG. 1B). The expandable member 140 is inflated until theexpandable member 140 exerts a force against an interior surface of thecannula 102 sufficient to prevent relative movement between the distalend 134 of the shaft 130 and the distal end 106 of the cannula 106during use of the steering device 120. After the distal end 134 of theshaft 130 has been secured to the cannula 102, the cannula 102 is theninserted into a body, and the proximal end 132 of the shaft 130 can bemanipulated to change a shape of the distal end 106 of the cannula 102to thereby steer the distal end 106. Particularly, pulling the proximalend 132 of the shaft 130 proximally will apply tension to the shaft 130,thereby causing the distal end 106 of the cannula 102 to bend, andreleasing the tension in the shaft 130 will cause the distal end 106 ofthe cannula 102 to return to its original shape.

After the distal end 106 of the cannula 102 has been steered to adesired site within a body, the expandable member 140 is then deflated,and the steering device 120 can be removed from the lumen 108 of thecannula 102. The lumen 108 can then be used to deliver a tool, aninstrument, a therapeutic element (such as a vaso-occlusive device, astent, or a radiation seed), a diagnostic element, or a fluid.

In the illustrated embodiment, inflation of the expandable member 140causes an axis 160 of the shaft 130 to offset from a center 162 of thecannula 102 at an axial position where the expandable member 140 islocated. This can be accomplished by making a wall of a portion of theexpandable member 140 relatively thicker than an adjacent portion. Asthe expandable member 140 is inflated, the thinner portion of theexpandable member 140 will expand or stretch relatively more than thethicker portion of the expandable member 140. Such configurationprovides a biased direction of a bending of the distal end 106, therebyallowing a physician to determine a direction in which the distal end106 of the cannula 102 will bend upon pulling of the shaft 130. In theillustrated embodiment, the expandable member 140 substantially occupiesthe lumen 108 at a cross section of the cannula 102. Alternatively, theexpandable member 140 can have other cross sectional shape, such that anelliptical shape (FIG. 1C), after it is inflated, such that theexpandable member 140 does not completely occupies the lumen 108 at across section of the cannula 102. Such configuration allows the cannula102 to deliver fluid or a tool even after the distal end 134 of theshaft 130 has been secured to the cannula 102.

FIG. 2 shows another catheter 200 in accordance with an embodiment ofthe invention. The catheter 200 includes a cannula 202 having a proximalend 204, a distal end 206, and a lumen 208 extending therebetween. Thecatheter 200 also includes a steering device 220 having an expandablemember 240. The cannula 202 and the steering device 220 are similar tothe cannula 102 and the steering device 120 discussed previously, exceptthat the lumen 208 of the cannula 102 is offset from a center 270 of thecannula 202. In such case, the expandable member 240 is configured toexpand uniformly radially at a cross section such that an axis 260 of ashaft 230 of the steering device 220 is not substantially offset from acenter 262 of the expandable member 240. The offset of the lumen 208from the center 270 of the cannula 202 provides a biased direction of abending of the distal end 202. Alternatively, the expandable member 240can have a configuration that is similar to that of FIG. 1B, such thatthe axis 260 of the shaft 230 can be further offset from the center 270of the cannula 202 after inflation of the expandable member 240.

It should be noted that the manner in which the steering device issecured to the cannula is not necessarily limited to the embodimentsdiscussed previously, and that a variety of securing mechanisms can beemployed. FIGS. 3A and 3B illustrate a catheter 300 in accordance withanother embodiment of the invention. The catheter 300 includes a cannula302 and a wire 320. The cannula 302 has a proximal end 304, a distal end306, and a lumen 308 extending therebetween. The cannula 302 alsoincludes an expandable member 330 and an inflation lumen 340 fordelivering fluid to inflate the expandable member 330. In theillustrated embodiment, the expandable member 330 is constructed as aportion of a wall 332 of the cannula 302 that is relatively thinner thanan adjacent portion of the wall 332. Alternatively, the expandablemember 330 can be a membrane that covers and seals an opening at thewall 332 of the cannula 302. The membrane can be made of a polymer orother elastic materials.

During use, the wire 320 is inserted into the lumen 308 of the cannula302 and is advanced distally until a distal end 322 of the wire 320reaches the distal end 306 of the cannula 302. Inflation fluid is thendelivered via the lumen 340 to cause the expandable member 330 to expandradially inwardly within the lumen 308. The expandable member 330 isexpanded until it compresses the wire 320 against an interior wall ofthe cannula 302 with a force sufficient to prevent the wire 320 frommoving relative to the distal end 306 (FIG. 3B). In the illustratedembodiment, the wire 320 includes an anchor member 324 in a form of asphere that is secured to the distal end 322. The anchor member 324 isconfigured to provide additional anchorage of the wire 320 against theinflated expandable member 330 during use. Alternatively, the anchormember 324 can have other shapes or configurations. For example, inanother embodiment, the anchor member 324 can be formed by bending thedistal end 322 of the wire 320.

After the wire 320 has been secured to the cannula 302, the cannula 302is then inserted into a body, and the wire 320 can be manipulated tosteer the distal end 306 of the cannula 302 until the distal end 306reaches a desired site. The expandable member 330 is then deflated toits unexpanded configuration to release the wire 320. After the wire 320is removed from the lumen 308 of the cannula 302, the lumen 308 can beused to deliver a tool, an instrument, a therapeutic element (such as avaso-occlusive device, a stent, or a radiation seed), a diagnosticelement, or fluid, as similarly discussed previously.

FIGS. 4A and 4B illustrates a catheter 400 in accordance with anotherembodiment of the invention. The catheter 400 includes a cannula 402 anda steering device 420. The cannula 402 has a proximal end 404, a distalend 406, and a lumen 408 extending therebetween. A wall 410 of thecannula 402 at the distal end 406 is relatively thinner than an adjacentwall 412, thereby creating a recess 414. The steering device 420includes a shaft 422 having a proximal end 424, a distal end 426, and alumen 425 extending therebetween, and an anchor member 428 secured tothe distal end 426. The steering device 420 also includes a filament430, such as a wire or a string, disposed within the lumen 425, and issecured to a portion 429 of the anchor member 428. The anchor member 428can be bent into a low profile (FIG. 4A), and can assume an opened orexpanded configuration when a bending force is removed or reduced. Theanchor member 428 is made from an elastic material, such as nitinol,stainless steel, or a plastic. In the illustrated embodiment, the anchormember 428 is secured to the distal end 426 by a suitable adhesive.Alternatively, the anchor member 428 can be an extension of the shaft422 that is fabricated together with the shaft 422 as a single unit.

During use, tension is applied to the filament 430 to bent the anchormember 428 into a low profile (FIG. 4A), and the steering device 420 isthen inserted into the lumen 408 of the cannula 402. The anchor member428 is advanced distally until it reaches the distal end 406. Thetension in the filament 430 is then released to allow the anchor member428 to assume an opened configuration, thereby anchoring the portion 429against the recess 414 (FIG. 4B). Alternatively, instead of applying atension force to the filament 430, the anchor member 428 can be insertedinto the lumen 408 and allows an interior surface of the wall 412 tocompress or bent the anchor member 428. In such case, the anchor member428 is advanced distally until it passes the recess 414, at which point,the anchor member 428 will spring open and anchor itself against therecess 414. After the steering device 420 has been secured to thecannula 402, it can be used to steer the distal end 406 of the cannula402 as similarly discussed previously. When it is desired to remove thesteering device 420, tension force can be applied to the filament 430 tobent the anchor member 428 into a low profile to disengage the anchormember 428 from the recess 414. The steering device 420 can then beremoved from the lumen 408 of the cannula 402.

FIGS. 5A and 5B show another variation of a steering device 520 that canbe used to detachably secure to a cannula to provide steeringfunctionality to the cannula. The steering device 520 includes a shaft522 having a proximal end 524, a distal end 526, and a lumen 528extending therebetween. A wall 530 of the shaft 522 is relativelythinner than an adjacent wall. The steering device 520 also includes awire 532 having a distal end 534 secured to the distal end 526 of theshaft 522, and a proximal end 536 secured to a handle 538. The wire 532is made of an elastic material, such as nitinol, and has an expandedconfiguration (FIG. 5B). When using the device 520, tension force isapplied to the wire 532 to stretch the wire 532 into a substantiallylinear profile (FIG. 5A). The device 520 is then inserted into a lumenof a cannula, and is advanced until the distal end 526 is desirablyplace. Next, the tension force in the wire 532 is reduced or removed(e.g., by releasing the handle 538), thereby allowing the wire 532 toassume the expanded configuration. The wire 532 pushes the wall 530radially outward and compresses against an interior wall of the lumen ofthe cannula, thereby securing the device 520 to the cannula. The device520 can then be used to steer a distal end of the cannula (e.g., bypulling the proximal end 524) as similarly discussed previously.

It should be noted that the manner in which the steering device isdetachably secured to the cannula should not be limited to the examplesdiscussed previously, and that a variety of securing mechanisms can beemployed. For examples, in alternative embodiments, the steering devicecan include a screw, a snap-fit connector, a frictional type connector,or other securing mechanisms for detachably securing the steering deviceto the cannula. Also, in alternative embodiments, the steering device orthe cannula can include a locking mechanism made from an elastic orsupper elastic material (e.g., Nitinol or polymer(s)), thereby allowingthe steering device to be detachably secured to the cannula by achanging shape of the locking mechanism.

In the previously described embodiments, the catheter includes onesteering device. Alternatively, any of the embodiments of the catheterdescribed previously can include one or more additional steering devicesthat can be inserted in one or more additional lumens of a cannula. Inaddition, any of the cannulas described previously can further include aworking channel such that the steering device can remain secured to thecannula while the working channel is used to deliver objects or fluid.FIG. 6 shows a catheter 600 that includes a cannula 602, a firststeering device 620, and a second steering device 622. The cannula 602has a proximal end 604, a distal end 606, and a working channel 607, afirst and a second lumens 608, 610 extending therebetween. The steeringdevices 620, 622 are similar to that described with reference to FIGS.1A and 1B. The steering devices 620, 622 are configured to be insertedinto the lumens 608, 610, respectively, and can be secured to thecannula 602, as similarly discussed previously. In the illustratedembodiment, the first and second lumens 608, 610 are spaced 180° fromeach other. Such configuration allows a bi-directional steering of thedistal end 606 of the cannula 602 in opposite directions by selectivelyapplying tension to either the first steering device 620 or the secondsteering device 622. Alternatively, the first and second lumens 608, 610can be spaced at other angles. Although only two steering devices 620,622 are shown, in alternative embodiments, the catheter 600 can includemore than two lumens for housing more than two steering devices 620,622, thereby allowing steering of the distal end 606 in more than twodirections.

During use, the steering devices 620, 622 are inserted into the lumens608, 610 of the cannula 602, and are secured to the cannula 602. Thedistal end 606 of the cannula 602 is then inserted into a body and issteered by pulling either of the steering devices 620, 622. When thedistal end 606 reaches a desired position, the first and the secondsteering devices 620, 622 can remain secured to the cannula 602, whilethe working channel 607 can be used to deliver an object or fluid. In analternative embodiment, the cannula 602 does not include the workingchannel 607. In such case, after the distal end 606 has been desirablypositioned within the body, one or both of the steering devices 620, 622can be removed from the lumens, 608, 610, respectively, and theunoccupied lumen(s) can be used to deliver an object or fluid, assimilarly described previously.

Although the steering devices have been described as being detachablysecured to a cannula such that the steering device does not sliderelative to the cannula, the scope of the invention should not be solimited. FIGS. 7A and 7B illustrate a catheter 700 in accordance withanother embodiment of the invention. The catheter 700 includes a cannula702 and a steering device 720 that is configured to be slidable relativeto the cannula 702 for steering the cannula 702. The cannula 702 has aproximal end 704, a distal end 706, and a lumen 708 extendingtherebetween. The steering device 720 includes a wire 722 having a bentdistal end 724.

During use, the wire 722 is at least partially inserted into the lumen708 of the cannula 702, and the cannula 702 is inserted into a body. Thedistal end 706 can be steered by sliding the distal end 724 of the wire722 either distally or proximally relative to the cannula 702.Particularly, when the bent distal end 724 is confined within the lumen708 and is located away from the distal end 706 of the cannula 702, thedistal end 724 is stretched or compressed into a low profile. When thebent distal end 724 is placed adjacent the distal end 706 of the cannula702, the stiffness of the bent distal end 724 predominates the stiffnessof the distal end 706 of the cannula 702, thereby causing the cannula702 to bend in a direction of the bent distal end 724 (FIG. 7B). When itis desirable to steer the distal end 706 in a different direction, thewire 722 can be retrieved proximally, rotated about an axis 730 suchthat the bent distal end 724 is oriented in a different radialdirection, and re-inserted into the lumen 708. In an alternativeembodiment, the distal end 706 of the cannula 702 can be made relativelymore flexible than a proximal portion of the cannula 702 (e.g., byconstructing a distal portion of the cannula 702 using a material thatis more flexible that that for a proximal portion) to thereby allow easeof bending at the distal end 706.

It should be noted that besides providing steering functionality to acannula, any of the steering devices described previously can also beused as a stiffening element to increase a stiffness (e.g., bendingstiffness, axial stiffness, and torsional stiffness) of a cannula. Inthis sense, the device (e.g., device 120, 220, 320, 420, 520, 620, 622,or 720) functions as a reinforcing when placed within a lumen of acannula. It should be noted that when any of these devices is being usedas a stiffening element, the device can be secured or unsecured to thecannula. FIG. 8 shows a catheter 800 having a cannula 802, a firststiffening element 820, and a second stiffening element 822. The cannula802 has a proximal end 804, a distal end 806, and a first and a secondlumens 808, 810 and a working channel 812 extending therebetween. Theworking channel 812 can be used to deliver a tool, an instrument, atherapeutic element, a diagnostic element, or fluid, as similarlydiscussed previously. The stiffening elements 820, 822 each includes anelongate member 830 (e.g., a wire, a fiber, a coil, or other structuresthat can function as reinforcing) having a distal end 832, and acoupling device 834 secured to the distal end 832. The coupling device834 has a slanted planar surface 835 that is configured to mate with aslanted surface 840 located within each of the lumens 808, 810. Suchconfiguration improves a torsional stiffness of the cannula 802, andallows a higher level of torsional (or torqueing) force be transmittedfrom the proximal end 804 to the distal end 806.

Although particular embodiments of the present inventions have beenshown and described, it will be understood that it is not intended tolimit the present inventions to the preferred embodiments, and it willbe obvious to those skilled in the art that various changes andmodifications may be made without departing from the spirit and scope ofthe present inventions. For example, instead of securing asteering/stiffening device to a distal end of a cannula, thesteering/stiffening device can be secured to the cannula at otherlocations along its length. In addition, instead of having only onesecuring mechanism, in alternative embodiments, any of thesteering/stiffening devices described previously can have a plurality ofsecuring mechanisms located along its length, thereby allowing thesteering/stiffening device to be secured to the cannula at multiplelocations along a length of the cannula. Furthermore, in alternativeembodiments, any of the cannulas described previously can furtherinclude additional lumen(s) or channel(s) for housing fiber optics,which can be used to deliver light energy to a distal end of thecannula, and/or collect image signals at the distal end of the cannula.

The specification and drawings are, accordingly, to be regarded in anillustrative rather than restrictive sense. The present inventions areintended to cover alternatives, modifications, and equivalents, whichmay be included within the spirit and scope of the present inventions asdefined by the claims.

1. A method for accessing a site within a body, comprising: inserting aflexible cannula into a body; inserting a distal end of a first elongatemember into a first lumen of the cannula; detachably attaching thedistal end of the first elongate member to the cannula; steering thedistal end of the cannula to a desired site in the body by manipulatinga proximal end of the first elongate member, said manipulationcomprising pulling the proximal end of the first elongate memberrelative to the cannula; detaching the distal end of the first elongatemember from the cannula, and removing the first elongate member from thefirst lumen of the cannula; and delivering an object or substance to thebody site through the first cannula lumen, wherein the object orsubstance is delivered through the first lumen after the first elongatemember has been removed.
 2. The method of claim 1, wherein the object isselected from the group consisting of at least a portion of a guidewire,at least a portion of an ablation device, at least a portion of animaging device, an optical fiber, a therapeutic element, a diagnosticelement, and an implant.
 3. The method of claim 1, wherein the cannulahas a second lumen extending between ends of the cannula, the methodfurther comprising delivering an object or substance to the body sitethrough the second cannula lumen.
 4. The method of claim 3, wherein theobject is selected from the group consisting of at least a portion of aguidewire, at least a portion of an ablation device, at least a portionof an imaging device, an optical fiber, a therapeutic element, adiagnostic element, and an implant.
 5. The method of claim 1, furthercomprising inserting a distal end of a second elongate member into asecond lumen of the cannula, and attaching the distal end of the secondelongate member to the cannula.
 6. A method for accessing a site withina body, comprising: inserting a flexible cannula into a body; insertinga distal end of a first elongate member into a first lumen of thecannula to thereby stiffen at least a portion of the cannula; detachablyattaching the distal end of the first elongate member to the cannula;manipulating a proximal end of the cannula to thereby place the distalend of the cannula at a desired position in the body, wherein saidmanipulation comprises one of applying tension to the first elongatemember or releasing tension in the first elongate member; detaching thedistal end of the first elongate member from the cannula, and removingthe first elongate member from the first lumen of the cannula; anddelivering an object or substance to the body through the first cannulalumen, wherein the object or substance is delivered through the firstlumen after the first elongate member has been removed.
 7. The method ofclaim 6, wherein the object is selected from the group consisting of atleast a portion of a guidewire, at least a portion of an ablationdevice, at least a portion of an imaging device, an optical fiber, atherapeutic element, a diagnostic element, and an implant.
 8. The methodof claim 6, wherein the cannula has a second lumen extending betweenends of the cannula, the method further comprising delivering an objector substance to the body site through the second cannula lumen.
 9. Themethod of claim 8, wherein the object is selected from the groupconsisting of at least a portion of a guidewire, at least a portion ofan ablation device, at least a portion of an imaging device, an opticalfiber, a therapeutic element, a diagnostic element, and an implant. 10.The method of claim 6, further comprising inserting a distal end of asecond elongate member into a second lumen of the cannula, and attachingthe distal end of the second elongate member to the cannula.
 11. Themethod of claim 1, wherein the distal end of the first elongate memberis detachably attached to the cannula by inflating an expandable memberdisposed on the first elongate member.
 12. The method of claim 1,wherein the distal end of the first elongate member is detachablyattached to the cannula by inflating an expandable member disposed onthe cannula.
 13. The method of claim 6, wherein the distal end of thefirst elongate member is detachably attached to the cannula by inflatingan expandable member disposed on the first elongate member.
 14. Themethod of claim 6, wherein the distal end of the first elongate memberis detachably attached to the cannula by inflating an expandable memberdisposed on the cannula.
 15. A method for accessing a site within abody, comprising: inserting a flexible cannula into a body; inserting adistal end of a first elongate member into a first lumen of the cannulato thereby stiffen at least a portion of the cannula; detachablyattaching the distal end of the first elongate member to the cannula;inserting a distal end of a second elongate member into a second lumenof the cannula, and attaching the distal end of the second elongatemember to the cannula; manipulating a proximal end of the cannula tothereby place the distal end of the cannula at a desired position in thebody, wherein said manipulation comprises one of applying tension to thefirst or second elongate members or releasing tension in the first orsecond elongate members; and delivering an object or substance to thebody through a working lumen of the catheter.